Acoustical and thermal insulators and liners for application to vehicles are well known in the art. These insulators typically rely upon both sound absorption, i.e. the ability to absorb incident sound waves and transmission loss, i.e. the ability to reflect incident sound waves, in order to provide sound attenuation. They also rely upon thermal shielding properties to prevent or reduce the transmission of heat from various heat sources (e.g. engine, transmission and exhaust system), to the passenger compartment of the vehicle. Such insulation is commonly employed as an under carpet heat shield and a floor pan insulator.
Examples of acoustical and thermal insulation in the form of liners are disclosed in a number of prior art patents including U.S. Pat. No. 4,851,283 to Holtrop et al. and U.S. Pat. No. 6,008,149 to Copperwheat. As should be apparent from a review of these two patents, engineers have generally found it necessary to construct such liners from a laminate incorporating (a) one or more layers to provide the desired acoustical and thermal insulating properties and (b) one or more additional layers to provide the desired mechanical strength and rigidity which allow simple and convenient installation as well as reliable and proper functional performance over a long service life.
While a number of adhesives, adhesive webs and binding fibers have been specifically developed over the years to secure the various layers of the laminates together, laminated shields and insulators have an inherent risk of delamination and failure. The potential is, in fact, significant mainly due to the harsh operating environment to which the shields and insulators are subjected. Many shields and insulators are located near and/or are designed to shield high heat sources such as the engine, transmission and exhaust system. As a result, the shields and insulators are often subjected to temperatures in excess of 200° F. which have a tendency to degrade the adhesives and binders over time.
Additionally, many shields and insulators are subjected to water from the surface of the roadways which has a tendency to be drawn by capillary action into the interface between the layers of the shields and the insulators. Such water may have a deleterious effect upon the integrity of the adhesive layer over time. This is particularly evident when one considers that water may also include in solution salt or other chemicals from the roadway which are corrosive and destructive.
A need is therefore identified for a trim panel insulator incorporating a nonlaminate acoustical and thermal insulating layer of polymer fibers suitable capable of providing the desired acoustical and thermal insulating properties. Advantageously, such an insulator also provides the desired mechanical strength and rigidity to allow simple and convenient installation while also providing a long service life characterized by reliable performance.